Even the Duggan blocks break and split apart with as little as 600 HP even in N/A trim, but far less than what the cast iron block can stand. So far only the billet blocks seem to withstand repeated use with HP and RPM. Just consider a cast iron block being a grenade with the pin pulled at the current power levels that are capable with today's power adders.
at 900hp its 5X to 6X the factory rating... think you ran out of engineering over design...
